The invention is based on an electro-magnetically operable valve for a fuel injection device for internal combustion engines. A valve is already known wherein a stop face provided on the magnet core has the same radius as an attracted ball which serves as part of the valve and as an armature. This causes an undesirable slowing of the closing movement of the ball, the latter having a tendency to stick to the core after the end of the excitation of the magnetic coil. This leads to an undesirable effect on the amount of medium to be controlled.